Selenocysteine‐Mediated Native Chemical Ligation

Abstract

C-Terminal peptide thioesters are shown to react efficiently with peptide fragments containing an N-terminal selenocysteine to give selenoproteins. In analogy to the native chemical ligation of thioesters and peptides containing N-terminal cysteines, the selenol presumably attacks the thioester nucleophilically to give a selenoester intermediate that subsequently rearranges to give a native chemical bond. The utility of this procedure was demonstrated by the synthesis of a selenium-containing derivative of bovine pancreatic trypsin inhibitor (BPTI) in which Cys38 is replaced by selenocysteine. The artificial selenoprotein folds into a conformation similar to that of wild-type BPTI and inhibits trypsin and chymotrypsin with unaltered affinity.